What a great Idea of building a mobile app for transport sector! I guess it can also track the cars/bus/trains in this app. This could help the basic necessities of the users because every day, they have to use transportation.
Since your back end is already fine, I suppose that you got really good ideas in your application. You know how the screens should look like, and so I want to see your style guide and I can give you suggestions about it. You plan really well, from your idea, you developed your back end, created style guide and now, for final UI design.
Just to let you know, we recently worked with a fresh startup from sanfasico called Paralign the app was a huge sucsess and they now have active 10,000 users already on there platform. We can also do the same, collaborate and create solution to be one of the top-notch apps.